The Case for Early Chemotherapy for the Treatment of Metastatic Disease

TP53INP1 as new therapeutic target in castration-resistant prostate cancer

BACKGROUND

Prostate cancer (PC) is one of the most common malignancies in industrialized countries, and the second leading cause of cancer-related death in the United States. We recently showed that over-expression of tumor protein 53-induced nuclear protein 1 (TP53INP1), a cell stress response protein, is a worse prognostic factor in PC, particularly predictive of biological cancer relapse. Moreover, treatment of castration-sensitive (CS) LNCaP tumor cells with a TP53INP1 antisense oligonucleotide (TP53INP1 ASO) inhibits proliferation and induces apoptosis. The aim of this study was to investigate variations of TP53INP1 expression in PC during androgen withdrawal therapy and in castration-resistant prostate cancer (CRPC).

METHODS

Quantitative measurements of immunohistochemical expression of TP53INP1 using high-throughput densitometry, assessed on digitized microscopic tissue micro-array images were correlated with hormone therapy (HT) status in human PC. Northern blot analysis of TP53INP1 after castration was performed in LNCaP xenograft. Treatment of CR C4-2 tumor cells in vitro with TP53INP1 ASO was analyzed. We also analyzed the effect of TP53INP1 ASO treatment in vivo on tumor xenograft growth.

RESULTS

TP53INP1 protein expression decreases during HT and increases after HT in human CRPC. TP53INP1 mRNA increases significantly in CR tumors of LNCaP xenograft. Moreover, treatment of CR C4-2 cells with TP53INP1 ASO downregulates TP53INP1 protein level, inhibits proliferation, and induces apoptosis. Finally, in vivo, TP53INP1 ASO treatment significantly inhibits the tumoral progression of CR C4-2 xenograft and enhances docetaxel cytotoxicity.

CONCLUSIONS

These results suggest that TP53INP1 could be considered as a relevant-specific target for molecular therapy of CRPC.

From clinical trials to clinical practice: therapeutic cancer vaccines for the treatment of prostate cancer

Therapeutic options for patients with metastatic castration-resistant prostate cancer are increasing, spurring an urgent need to better understand which treatments are best for individual patients. The recent approval of a first-in-class agent, sipuleucel-T, has intensified this need. This therapeutic cancer vaccine has demonstrated a survival advantage in two Phase III trials, but does not alter progression in the short term. Therefore, a new therapeutic approach for patients with metastatic castration-resistant prostate cancer is taking shape, based on broader understanding of available therapies. This new clinical approach seeks to maximize patient benefit from treatment, minimize associated toxicities, and may have far-reaching implications for other therapeutic cancer vaccines currently in clinical development.

Depletion of intrinsic expression of Interleukin-8 in prostate cancer cells causes cell cycle arrest, spontaneous apoptosis and increases the efficacy of chemotherapeutic drugs

Background

The progression of all cancers is characterized by increased-cell proliferation and decreased-apoptosis. The androgen-independent prostate cancer (AIPC) is the terminal stage of the disease. Many chemokines and cytokines are suspects to cause this increased tumor cell survival that ultimately leads to resistance to therapy and demise of the host. The AIPC cells, but not androgen-responsive cells, constitutively express abundant amount of the pro-inflammatory chemokine, Interleukin-8 (IL-8). The mechanism of IL-8 mediated survival and therapeutic resistance in AIPC cells is unclear at present. The purpose of this report is to show the pervasive role of IL-8 in malignant progression of androgen-independent prostate cancer (AIPC) and to provide a potential new therapeutic avenue, using RNA interference.

Results

The functional consequence of IL-8 depletion in AIPC cells was investigated by RNA interference in two IL-8 secreting AIPC cell lines, PC-3 and DU145. The non-IL-8 secreting LNCaP and LAPC-4 cells served as controls. Cells were transfected with RISC-free siRNA (control) or validated-pool of IL-8 siRNA. Transfection with 50 nM IL-8 siRNA caused >95% depletion of IL-8 mRNA and >92% decrease in IL-8 protein. This reduction in IL-8 led to cell cycle arrest at G₁/S boundary and decreases in cell cycle-regulated proteins: Cyclin D1 and Cyclin B1 (both decreased >50%) and inhibition of ERK1/2 activity by >50%. Further, the spontaneous apoptosis was increased by >43% in IL-8 depleted cells, evidenced by increases in caspase-9 activation and cleaved-PARP. IL-8 depletion caused significant decreases in anti-apoptotic proteins, BCL-2, BCL-xL due to decrease in both mRNA and post-translational stability, and increased levels of pro-apoptotic BAX and BAD proteins. More significantly, depletion of intracellular IL-8 increased the cytotoxic activity of multiple chemotherapeutic drugs. Specifically, the cytotoxicity of Docetaxel, Staurosporine and Rapamycin increased significantly (>40% at IC₅₀ dose) in IL-8 depleted cells as compared to that in C-siRNA transfected cells.

Conclusion

These results show the pervasive role of IL-8 in promoting tumor cell survival, and resistance to cytotoxic drugs, regardless of the cytotoxic mechanism of antiproliferative drugs, and point to potential therapeutic significance of IL-8 depletion in men with AIPC.

Phase I/II study of biweekly paclitaxel and radiation in androgen-ablated locally advanced prostate cancer

PURPOSE

To determine the maximum-tolerated dose (MTD) of concurrent paclitaxel and radiation therapy (RT) in patients with locally advanced prostate cancer.

MATERIALS AND METHODS

Eligible patients had T2-4 tumors with Gleason scores greater than 7 and/or PSA levels greater than 10 ng/mL and/or had tumors with pathologic stage TxN1. Hormonal ablation was initiated 3 months before RT and was given for 9 months. RT was delivered daily (1.8 Gy) with concurrent twice-weekly paclitaxel (30 mg/m(2)). The whole pelvis was irradiated to 39.6 Gy. The radiation dose was escalated as follows: 63 Gy, 66.6 Gy, 70.2 Gy, and 73.8 Gy. The last RT dose level was fixed at 73.8 Gy.

RESULTS

Between January 2000 and October 2006, 22 patients were enrolled. The median age was 59 years (range, 48 to 72 years); the median PSA level was 22.4 ng/mL (range, 2.8 to 113 ng/mL). The number of patients per stage was as follows: three with T1, eight with T2, 11 with T3, and five with pN1 = 5. No grade 3 toxicities occurred at 63 Gy. Grade 3 diarrhea occurred in three patients at 66.6 Gy. The protocol then was amended to treat the prostate volume first followed by the whole pelvis. No grade 3 toxicities were observed at 70.2 Gy. One patient experienced grade 3 diarrhea at 73.8 Gy. Five additional patients were treated to 73.8 Gy without grade 3 toxicity, which established the MTD for combined paclitaxel and RT at 73.8 Gy. At 38 months median follow-up (range, 9 to 87 months), 21 (95%) of 22 patients are alive. Six (27%) of 22 experienced recurrence.

CONCLUSION

Concurrent biweekly paclitaxel with RT is feasible, with an MTD of 73.8 Gy. Recovery of gonadal function occurs in the majority of patients. These results encourage testing in a phase III setting.

Molecular targeting of Bcl-2 overcomes prostate cancer cell adaptation to XIAP gene downregulation

X-linked inhibitor of apoptosis (XIAP) is a suppressor of apoptosis that supports an increased survival and resistance to chemotherapy of human prostate cancer (PCa) cells. Effects of transient (24 h) and chronic (beyond 1 month) downregulation of XIAP in DU145 hormone refractory prostate cancer (HRPC) cells were studied. We found that transient downregulation of XIAP by siRNAs resulted in an increase of apoptosis and a decrease in Bcl-2 levels and sensitized PCa cells to cisplatin. XIAP downregulation by shRNA vector stable transfection led to upregulation of Bcl-2 protein. Our results identify the adaptability of PCa cells to chronic loss of XIAP in part through upregulation of Bcl-2 and indicate that multitargeting approach is the most effective application in the chemotherapy of human HRPC.

Prognostic and Predictive Factors in Patients with Androgen-Independent Prostate Cancer Treated with Docetaxel and Estramustine: A Single Institution Experience

OBJECTIVES

To investigate potential prognostic and predictive factors in patients with androgen-independent prostate cancer (AIPC) treated with docetaxel chemotherapy.

METHODS

This analysis included 94 consecutive AIPC patients who were treated between March 2001 and May 2006 with biweekly docetaxel 45 mg/m(2) (day 2) and estramustine 140 mg three dimes daily (days 1-3).

RESULTS

Prostate-specific antigen (PSA) responses were observed in 45 of 84 evaluable patients (53%), whereas objective responses were observed in 16 of 40 patients with measurable disease (40%). Median survival (OS) was 16.2 mo (95% confidence interval [CI], 12.9-19.4) and median time to PSA progression (TTP) 5.0 mo (95%CI, 3.6-7.1). OS was independently associated with pain score baseline PSA and weight loss. Patients with only extraosseous disease had higher PSA response rate (87% vs. 49%, p=0.014) and superior TTP compared with patients with bone metastases with or without extraosseous disease (7.3 vs. 4.3 vs. 4 mo, p=0.002). Concurrent bone and extraosseous metastases were associated with worse prognosis compared with each site alone (median OS: 12.3 vs.19 vs.18.3 mo, p=0.007).

CONCLUSIONS

Among patients with AIPC treated with biweekly docetaxel and estramustine, baseline PSA >100, existence of pain, weight loss, and simultaneous extraosseous and bone disease were associated with worse prognosis. Extraosseous metastases seem to be more sensitive than bone disease to this chemotherapy.